Alloy steel



Patented July 11, 1939 2,165,553

UNITED STATES PATIENT OFFICE ALLOY STEEL Daniel E. Krause and ClarenceH. Lorig, Columbus, Ohio, aasignors to Battelle Memorial Institute,Columbus, Ohio, a corporation of Ohio No Drawing. Application September7, 1937,

' Serial No. 162,695

Claims. (01. 15-425) Our invention relates to alloy steels. It has to Inspite of the rather remarkable influence of do, more particularly, withalloy steels which small amounts of phosphorus on the mechanical containphosphorus and vanadium. properties and corrosion resistance, as shownin The effect of phosphorus on corrosion and the above tables,phosphorus by itself may be mechanical properties of carbon steels andvarious objectionable in some cold-forming and coldalloy steels is wellknown. Its influence on drawing. steels because it increases theirhardatmospheric corrosion and corrosion in other ness. Furthermore, inexcess amounts it induces media is regarded as very beneficial. Byitself, cold-shortness, increases the size of the grain, or incombination with other elements, it funclowers the ductility and causessegregation in the tions as an alloy and strengthening element and,ingots into which the steels are cast. as such, produces high yieldstrength and yield One of the objects of our invention is to proratio.For the above reasons, many of the newly vide low alloy, high strengthsteels having greatly developed low-alloy, high yield strengthstrucimproved mechanical properties, reduced grain tural steels containsubstantial percentages of size, increased ductility, and increasedcorrosion phosphorus. resistance to the atmosphere.

The remarkably great effect upon mechanical Other objects will beapparent from the followproperties and corrosion resistance conferred oning description of our invention. steels by small additions ofphosphorus is demon- We have found that additions of vanadium to stratedby results obtained on a series of very low Phosphorus Steels greatlyimprove t e mechanicarbon steels containing increasing percentages .calproperties, reduce theirgrain size, increase of phosphorus. Normalizedbar stock of these their ductility, very materially increase theirsteels had mechanical properties shown in th corrosion resistance to theatmosphere, and in following table: other ways improve the phosphorussteels by 5 Base combo8ition 0 03% C, 010% Mn, 0 01% Si suppressing someof the detrimental influences o 047 S of excess phosphorus. Grain sizereductions and its control by the use of vanadium in phosphorus steelsassist in producing better steels of more 32, 31 $321,, gigg uniformproperties and with less segregation.

cent lb./sq. in. lbJsq. in. 2" 1.255% a. lb. As illustrative of thegrain size reduction brought about in phosphorus steels by vanadium, two

annealed sheet steels, each containing 0.12% car- .1, 8:92 {3% 3 3; gban and 0.17% phosphorus, one without vanadium 2 %,:g 42,000 40 7s 54and one containing 0.20% vanadium, had grain 5 2g 2-, i" counts of 4,000and 36,000 grains per sq. in., re-

spectively. Thus, a great decrease in grain size 35 Thus the abdveresults indicate phosphorus results from the use of vanadium inphosphorus h k Steels. x 2 5 eflect the mechanical We have found thatsteels containing less-than In 1 form 0.5% carbon, up to about 0.5%phosphorus and dicated steels s v vid igsizs fi xifiu z tie to about 05%vanadium readily workable atmosphere for 6 d 12 months as follows: 7both hot and cold and have decidedly better properties than steels ofthe same carbon and phosphorus content but containing no vanadium. Forbest resistance to corrosion, the carbon con- I tent should be less than0.25% and preferably 3,33 :33:25 it should be under 0.15%. The carboncontent may be as low as 0.01 per cent. The amount of phosphorus islimited only by its deleterious influences on other properties requiredof the steels.

Weight loss mgJcm.

O lbWNbass ss QWGOIOQ sass? QQQNN vanadium overcome to a degree thesedeleterious influences and therefore allow higher phos- Thus, the aboveresults indicate that an inphorus contents tobe used. While theresistan'e crease in the phosphorus content results in an into corrosionof steels is greatly improved if they crease in the corrosion resistanceof the steel. contain from 0.08% to 0.50% phosphorus, we 55 Lower carboncontents and the presence of prefer to use from 0.08% to 0.25%phosphorus.

We have discovered that in the presence of phosphorus, vanadium addsgreatly to the resistance to corrosion of steels. While we may usepercentages of vanadium as high as 0.5%, the cost of the element in someinstances renders its use to this extent inadvisable. We have found thatin the less costly steels, vanadium in percentages from 0.025% to 0.25%is satisfactory.

The remaining constituents of the steels, aside from iron, are thoseincidental to their manufacture. The sulphur is maintained low,preferably not more than 0.20%, though steels containing more than thisare within the scope of our invention. The manganese is maintained under1.5%. The preferred percentage of manganese is from 0.2% to 0.8%.

The following tables illustrate examples of steels made in accordancewith the present invention and compare them with other steels. Themechanical properties were obtained on bar stock after normalizing andafter annealing and the atmospheric corrosion losses were obtained on 22gauge sheet.

decidedly beneficial, although this amount of copper does not measurablyincrease the strength or raise the yield point. When the loss inmechanical strength, which would accompany a decrease in vanadiumcontent, is not of serious consequence in the use of the steel, then itbecomes possible to replace some of the much more costly vanadium withcopper without impairing the resistance to corrosion. In this case, theuse of 1 to 2 times as much copper as the vanadium which it replaceswould not'less'en the resistance to corrosion. On the other hand, 0.1%to 0.5% copper, in addition to the indicated vanadium content, can beused to further enhance the resistance to corrosion that resultsfrom thejoint use of phosphorus and vanadium.

When the strength and yield point of steels having combinations ofcarbon, phosphorus, vanadium and copper which are particularlysatisfactory are to be raised, we prefer to obtain the increasedstrength and yield point by the use of more copper rather than by theuse of additional amounts of one or more of the other three elements.This preference lies in the fact that cop- Tensile Yield Elong. Red. 01Charpy C, P, V, Cu, B 1 percent percent percent percent Condition151:5151; 106 :3611; tfi b f L- 03 21 Normalized 55,000 32, 500 44 75 672- 03 21 Annealed 52, 500 29, 500 44 75 7 3 .12 .17 63,000 39,500 38 6730 4-.-- .12 31 76, 000 51, 500 34 01 10 5 .25 .18 77,250 42,500 30 4914 6. 14 17 65,000 40, 000 3s e5 34 7 .14 .17 80,000 50,000 29 57 4 5 aat: a z; s 3 9- 12 .004 000 9,

10... 12 16 79,000 56,500 34 65 30 ll .12 I .16 73,000 50,000 34 65 2912 .03 .006 34,500 25,000 48 83 42 13--- 13 .008 50,250 32,000 42 72 5114--. .06 .25 .19 1.5 79, 100 63,300 67 31 15- 06 25 19 1. 5 Annealed-78, 000 62, 300 32 67 30 (0 Atmospheric corrosion weight loss mg/cm 0,P, V, Cu, percent percent percent percent Condition 6 months 12 monthsexposure exposure 1-... .03 .21 17.6 25.8 2.--- .03 .21 14.0 25.8 3 .12.31 16.8 23.6 4 12 31 14.0 21. 7 5---. .25 .18 17.2 21.2 8---- .14 .1716.3 22.2 7--.- .14 .17 16.0 22.7 8.--- .12 .004 21.0 31.0 it" '15 '32it? 24. 8 ML 11... .12 .10 13.1 21.4

The vanadium-phosphorus steels, having a substantial content of bothelements, are characterized by having very high tensile and yieldstrengths relative to the tensile andyield strengths of the phosphorussteels containing only traces of vanadium or the vanadium steels low inphosphorus. They are extremely ductile. In resistance to corrosion, thevanadium-phosphorus steels are superior to the copper-phosphorus steelsof the very high phosphorus types.

In some instances, part of the vanadium may be replaced by copper or thecorrosion resistance and mechanical properties of the steels may beenhanced by the use of copper in addition to the vanadium contentindicated above. .For corrosion resistance, the use of 0.1% to 0.5%copper,

76 in addition to the indicated vanadium content, is

per decreases the ductility'far less for a given increase in strengthand yield point than does additions of carbon or phosphorus in steelsalready containing carbon and phosphorus. In the presence of substantialamounts of phosphorus, more carbon is deleterious as it inducesbrittleness, while in a steel already containing substantial amounts ofphosphorus, an increase of phosphorus very seriously eiIects the impactresistance and ductility. The use of vanadium merely to strengthen thesteels, in most instances, is inadvisable because of its cost.

We have found that 1% copper will increase both the strength and yieldpoint of the steels from 5,000 to 20,000 lb./sq. in. depending upon theheat treatments given them, and that additional increases of the samemagnitude may be obtained through precipitation hardening. The lattermay be effected with normalized steels containing 0.7%

to 3% copper by holding them in, or cooling very slowly through theprecipitation hardening temperature range of 750 degrees to 1050 degreesF.

The. preferred range of copper for improved strength and yield point'isabout 0.50% to 3%.

Our steel has an advanta in welding. On welding thehardening in theadjacent to the weld is not apprecia a. One of the secondary advantagesof the v um in the steel is that it prevents a martensitic zone-fromforming in the steel near the weld. Another function of the vanadiumisto prevent grain .growth in the overheated zone adjacent to the weld.Phosphorus steel without vanadium will be coarse grained in this zone.

It will be apparent from the above description that we have providedphosphorus-vanadium steels having greatly -improved mechanical properties, reduced grain size, increased ductility and increased corrosionresistance. The steel will have a yield strength in therolled,normalized and annealed conditions of more than 40,000'lhs./sq. in, aductility at least equal to that of plain carbon steel of equalstrength, a small grain structure, and a resistance to atmosphericcorrosion that is greater than that of either plain phosphorus steel ofhire phosphorus content or phosphorus-copper steel of like phosphorusand copper content.

The phosphorus-vanadium steels with or without copper, of the typedisclosed herein, having high physical properties as well as highresistance to corrosion may be made into castings orcan-be fabricatedinto rough articles such as structural shapes, sheet, plate, wire andtubing which are to be used where resistance to corrosion, as well ashigh physical properties are desired.

Having thus described our invention, what we claim is:

1. An alloy, steel consisting of fr m 0.01% to ne immediately 0.5%carbon, from 0.025% to 0.5% vanadium,

from 0.08% to 0.5% phosphorus, from 0.2% to 1.5% manganese, copper in anamount not over 3%, and not over 0.20% sulphur, the balance beingsubstantially all iron. v

I 2. An alloy steel consisting of from 0.01% to 0.25% carbon, 0.025% to0.25% vanadium, 0.08%

'to 0.25% phosphorus, 0.2% to 0.8% manganese,

copper in an amount not over'3%, and not over 0.20%'sulphur, the balancebeing substantially all iron.

3. An alloy steel consisting of from 0.01% to 0.25% carbon, 0.025% to0.25% vanadium, 0.08% to 0.25% phosphorus, 0.2% to 0.8% manganese,

0.10% .\to0.5% copper, and not more than 0.20% sulphur, th balance beingsubstantially'all iron. 4. An allo steel containing from 0.01 .per centto 0.5 per cent'carbon, from 0.025 per cent to 0.5 per centvanadium,from 0.08 per cent to 0.5 per cent phosphorus, from 0.2 percent to 1.5 per cent 20 manganese, copper in an amount not over 3 percent, and not over 0.20 per cent sulphur, the phosphorus being presentfor the purpose of enhancing the corrosion resistance and mechanicalproperties of the steel and not merely as an impurity-and 25.

the vanadiumbeing present to oflset the embrit-- tling eifect ofphosphorus, the balance being substantially all iron, the steel having ayield strength in the rolled, normalized and annealed conditions of morethan 40,000 pounds per square inch and e ductility at least equal tothat of plain carbon steelpf equal strength.

I ,5. An alloy steel consisting of from 0.01% to

